tilizers er & of B i io B p f e o s l t i a c n i d r e u s o J Journal of Biofertilizers & Biopesticides Bekele, et al, J Biofertil Biopestici 2014, 5:2 ISSN: 2155-6202 DOI: 10.4172/2155-6202.1000144 Research Open Access Larvicidal and Adulticidal Effects of Extracts from Some Indigenous Plants against the Malaria Vector, Anopheles Arabiensis (Diptera: Culicidae) in Ethiopia Damtew Bekele1*, Beyene Petros2, Habte Tekie3 and Zemede Asfaw4 1Department of Biology, College of Natural Sciences, Debre Markos University, Ethiopia 2Department of Microbial, Cellular and Molecular Biology, College of Natural Sciences, Addis Ababa University, Ethiopia 3Department of Zoological Sciences, College of Natural Sciences, Addis Ababa University, Ethiopia 4Department of Plant Biology and Biodiversity Management, College of Natural Sciences, Addis Ababa University, Ethiopia *Corresponding author: Damtew Bekele, Department of Biology, College of Natural Sciences, Debre Markos University, Ethiopia, Tel: 0251-1-0912-179124; Fax: 058-7-716002; E-mail: [email protected] Rec date: Apr 23, 2014, Acc date: May 28, 2014, Pub date: May 31, 2014 Copyright: © 2014 Bekele D, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Abstract The mosquito Anopheles not only cause nuisance by their bites but also transmit deadly diseases like malaria in Sub-Saharan Africa, where most of the malaria deaths occur in the world. In Ethiopia, despite the use of native plants in traditional combat against mosquitoes, use in a modern way has remained scanty. The present study, being based on an initial ethno botanical survey, carried out screening experiments on five indigenous ethno botanical species (Aloe pirottae Berger, Aloaceae; Acokanthera schimperi (A.DC) Schweinf, Appocynaceae; Brassica nigra L. Koch, Brassicaceae; Oreosyce africana Hook.f., Cucurbitaceae and Piper capense L.f., Piperaceae). The larvicidal activity of 80% methanol extracts of the first two plant species against the fourth instars of Anopheles arabiensis Patton, and adulticidal activity with the same solvent extracts of the latter four species against Anopheles arabiensis adults, gave positive results upon evaluation under laboratory condition. The 80% methanol extract of the gel of A. pirottae had more activity within 24 hours on the larvae than the leaf extract of Acokanthera schimperi. The highest (100%) mortality in the fourth instars occurred on treatment with 160 ppm extract of Aloe pirottae and 480 ppm extract of Acokanthera schimperi. The maximum adult mortality was detected in the leaf extract of Oreosyce africana (LC50 18.74 and LC90 39.66 ppm) followed by fruit extract of Piper capense (LC50 24.30 and LC90 46.32 ppm), while no mortality was noticed in the control groups. Phytochemical screening of the methanol extracts of the leaves of Oreosyce africana and the fruits of Piper capense had key secondary metabolites (alkaloids, saponins, flavonoids, cardiac glycosides), further corroborating their adulticidal properties. These findings announce the first evidence that Aloe pirottae is a promising mosquito larvicide while Oreosyce africana and Piper capense carry huge potentials as mosquito adulticides contributing to integrated malaria control through proper mosquito management. Keywords: Indigenous plant extracts; Anopheles arabiensis; insecticide treated nets and indoor residual spraying that was found to Larvicide; Adulticide be effective as a control measure [7]. Mosquito resistance to the currently-used insecticides and the Introduction emergence of multi drug-resistant strains of parasites has escalated the Vector borne diseases are among the major causes of illness and malaria problem in the affected countries. According to the studies death in many developing countries. Mosquitoes (Diptera: Culicidae) conducted in Ethiopia [6,8-10], An. arabiensis was resistant to an array are responsible for transmitting the most important vector borne of insecticides, including DDT, permethrin, deltamethrin and diseases including malaria, lymphatic filariasis, Japanese encephalitis, malathion. Earlier report [11] has documented mosquito resistance to and dengue as well as yellow fever and other forms of encephalitis [1]. the four classes of insecticides. Thus, synthetic insecticides have Malaria is now responsible for illness in more than an estimated 300 created several problems including the development of resistant insect million people, resulting in one million deaths per year [2]. Malaria is strains, ecological imbalance and harm to mammals. These drawbacks transmitted through bites of parasite-infected Anopheles mosquitoes. of the hitherto developed insecticides, researchers in the area are The abbreviation for Anopheles arabiensis is An. arabiensis [3], which working hard to find environmentally safe alternatives. Botanical is the most important vector associated with the transmission of insecticides may serve as suitable alternatives to synthetics in future, as malaria disease. Anopheles arabiensis is the major malaria vector in they are relatively safe, degradable and readily available in many parts Ethiopia [4-6]. The approach to combat this disease largely relied on of the world [12]. For this, they resorted to plant extracts as potent interruption of the disease transmission cycle by either targeting the sources of natural biocides [13]. mosquito larvae through spraying of stagnant waters that serve as Although insecticides of plant origin have been extensively used on breeding sites or by killing the adult mosquitoes using insecticides. agricultural pests, a very limited extent has been used against insect The malaria control strategies in Ethiopia include the combination of vectors of public health importance [14]. Because of these many of the J Biofertil Biopestici Volume 5 • Issue 2 • 144 ISSN:2155-6202 JBFBP, an open access journal Citation: Bekele, Petros, Tekie and Asfaw (2014) Larvicidal and Adulticidal Effects of Extracts from Some Indigenous Plants against the Malaria Vector, Anopheles Arabiensis (Diptera: Culicidae) in Ethiopia. J Biofertil Biopestici 5: 144. doi:10.4172/2155-6202.1000144 Page 2 of 8 reported tropical plants came under scrutiny, leading to extraction and (B. nigra) and fruit extracts of Piper capense (P. capense) were checked characterization of their active constituents, which accounted for for its efficacy as an adulticide against the same vector. various uses by people. Among the most important constituents are alkaloids, terpenoids, steroids, phenols, saponins and tannins [15]. Materials and Methods Mosquito controls strategies; especially those that are effective, cheap and environmentally non-hazardous are needed. Hence, crude plant Selection and collection of plant material extracts have played an important role in this aspect. One of the most studied botanical species with good pesticides attributes is the neem For the present study, five different plant species were selected from tree (Azadirachta indica A. Juss.), whose extracts have shown different regions of Ethiopia. Plant selection in the study was based on considerable activity and multiple modes of action against agricultural interviewing traditional herbalists and members of the community to pests, forestry insects, and insects of public health [16]. specify the indigenous plant species known for their use in the regular control of mosquitoes and other insects in their localities, and through Many herbal products have been used as natural insecticides before analysis of the relevant literature. To select the most relevant and the discovery of synthetic organic insecticides [17]. And a wide range promising species for purpose of chemical screening, all the candidate of plants with larvicidal and adulticidal properties have been used plants were ranked following the application of weighted criteria as against insects [18]. In Ethiopia, about 1000 higher plants are described by Martin [22]. By combining the ethno botanical leads and employed in the traditional healthcare and that 60% of them are said chemotaxonomic evidence (popularity of plants already used as to be indigenous and the same proportion is believed to have healing insecticides by local people and documented evidence of insecticidal potentials [19]. Prevention of malaria and other diseases is commonly constituents in the family to which the candidate species belongs) practiced by indigenous people using traditional insecticides and highly promising plant species are selected for testing. Following such insect repellent plants. For example, a study conducted by Berhanu et procedure provided useful information essential for further evaluation al. [20] showed that Allium sativum Linn is the most widely used of larvicidal and adulticidal activities of the few priority plants tested mosquito repellent followed by Lepidium sativum L. and Capparis against An. arabiensis. Once the priority plants are identified, the next tomentossa Lam. In addition to being readily available in different step involves isolating and identifying the new bioactive chemical parts of the country, locally growing plants are economically more compounds present in the indigenous plant species that might possess viable and the methods employed are usually simpler. Though several superior larvicidal/adulticidal properties. compounds of plant origin have been reported
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